Hot-work steel tested in die casting molds for the automotive industry

The German stainless steel works, German subsidiary of Schmolz + Bickenbach Group, have expanded their range of products. Since March, the new Hot-work steel “ThermodurE 40 K Superclean” is now available in all dimensions from 800 x 100 to 800 x 400 mm – also in machined form on request. Nemak’s Polish branch is currently testing the steel as a material for the inserts of die-casting molds in which 4-cylinderEngine blocks should be created.

“The material has attracted great interest because it delays the formation of hot cracks and thus significantly increases the service life of the tool compared to proven hot-work steels,” explains Hans-Georg Maschetzke, Sales Manager Tool Steel EU Enduser at Deutsche Edelstahlwerke.

Currently, Nemak's Polish branch is testing the steel as a material for the inserts of die-casting molds that will later be used to produce 4-cylinder engine blocks. 300 kg is the weight of a single cuboid or cube-shaped insert. "The toughness and thermal shock resistance of the material are most important to us because these two properties have a decisive influence on the speed of hot cracking," explains the management of Nemak, Poland.

Two million castings a year

Every year, the companies in Bielsko-Biala, Poland, produce around two million castings for the automotive industry. In the future, the company also wants to further expand the production of aluminum structural parts, which is important in automotive engineering, at its Polish site. The cost-effectiveness of production and the quality of the subsequent die-cast components depend largely on the tool material.

"Our automotive customers place the highest demands on our cast parts. In particular, they expect flawless surfaces and absolutely precise geometries. The basis for this is a tool made of hot-work steel that is tailored to this purpose," says the head of the toolmaking department at Nemak Poland.

High expectations in the test phase

The mold inserts, which give the later cast part the desired characteristic shape and complexity, are exposed to an extreme environment during the production of aluminum die casting. It takes just two minutes to produce a part. The mold inserts have to withstand high pressures and temperatures of over 700 °C. "The thermal shock cracks that occur sooner or later cannot be prevented, only delayed, as the ThermodurE 40 K Superclean very effectively. Sooner or later they lead to the failure of the mold, because when the cracks grow together and breakouts occur, these would be transferred to the surface of the die-cast part produced," says Sales Manager Maschetzke.

Nemak also confirms this. The company is now testing the mold inserts made of ThermodurE 40 K Superclean under real operating conditions. “The entire test phase lasts a good year. We compare the parameters determined afterwards with the previous values. We look closely at the surface finish, which has a direct and decisive influence on the service life of the tool as a whole. So far, we have used Engine and gearbox housings the ThermodurE 38 K Superclean from Deutsche Edelstahlwerke, which has proven itself for us,” reports management.

Expectations for the new material are therefore high. No wonder, since the company has so far produced an average of 80.000 to 150.000 die-cast parts with one set of mold inserts. Using the new hot-work steel from Deutsche Edelstahlwerke, the material may only show very slight cracking after 60.000 die-cast parts. With other materials, this should already be much more pronounced by this point. Material breakouts after 100.000 pieces are completely taboo.

"We expect, among other things, that the ThermodurE 40 K Superclean will enable us to significantly reduce maintenance costs, which arise, for example, when repairing the inserts by welding. These maintenance measures are necessary in order to be able to fully exploit the service life of the mold frame economically. As a rule, we take a mold frame out of production after the inserts have been changed three times," adds the head of the toolmaking department at Nemak Poland.

Full service creates trust and success

From longer tool life to lower maintenance costs and more flexibility in die-casting production through to reliable, high-quality delivery performance for die-casting manufacturers and automotive customers – the expectations are high, and so is the optimism that the cooperation will once again be crowned with success.

The start of the test phase went according to plan. Deutsche Edelstahlwerke has been supplying its customer Nemak with tool steel for mold frames and mold inserts for 15 years. Around 400 t reach the Polish companies directly by truck every year. The largest share is made up of mold frames weighing up to 16 t made of Formadur2312, Formadur2738 and Formadur320, which the steel producer delivers ready for installation.

“In addition to the reliable steel quality, good technical advice is an important criterion for us, especially for new projects, which always convinces us for the German stainless steel works as suppliers and competence partners. There is a regular exchange of experience between the technical experts on both sides at numerous on-site meetings," says Nemak management, explaining the fruitful cooperation.

This of course also applies to the test phase with the new ThermodurE 40 K Superclean, in which Deutsche Edelstahlwerke is a full-service provider: starting with technical customer advice, through steel production and processing at the Witten site, to hardening in the company's own hardening plants in Lüdenscheid. "Close cooperation with the experts is particularly important when developing the optimal heat treatment for our purposes."

They are pleased with the trust that the renowned die-casting manufacturer has placed in them. “The further improved temperature resistance compared to ThermodurE 38 K Superclean without a significant Reduction of toughness, make the E 40 K Superclean interesting for all die-casting producers who have to meet both the increasing quality requirements of their customers and their own efficiency requirements," concludes Hans-Georg Maschetzke.